Gil Eshel

Reflectance Spectroscopy as a Tool for Monitoring Contaminated Soils

Soil reflectance spectroscopy is a well-known technique to assess soil properties rapidly and quantitatively in both point (spectroscopy) and spatial (imaging spectroscopy (IS)) domains. The quantitative approach has been developed in the past two decades by many researchers, with much literature on the topic. Basically, this approach was adopted from other disciplines (e.g. food, textiles), whereas the mapping approach was incorporated with spectral-based remote sensing means. Soil contamination is an ever-growing concern, and a reliable and environmentally friendly method is needed to rapidly detect and monitor soil contaminants at any stage for the diagnosis of suspected contaminated areas, as well as for controlling rehabilitation processes. Conventional methods for investigating soil contamination based on point sampling and chemical analysis are time-consuming, costly and sometimes incorporate the use of environmentally damaging chemicals. Soil reflectance spectroscopy is a promising tool for the efficient detection and monitoring of soil contaminants. Using reflectance spectroscopy measurements, several direct and indirect soil properties, as well as soil contamination characteristics, can be extracted. Due to the vast amount of data in soil spectroscopy, be it point or image, data-modeling processes are required. This chapter reviews soil spectroscopy theory and its quantitative capabilities, as well as data-modeling methods for soil spectra that are related to soil contamination. Discussed contaminants include petroleum hydrocarbons, heavy metals such as Ni, Cr, Cu, Cd, Hg, Pb, Zn and As, acid mine drainage and pesticides. Limitations, obstacles and problems in recording soil spectra in the field and in the laboratory are discussed, along with IS technology. The future potential of spectral technology and IS missions used for soil contamination monitoring is presented, based on ongoing worldwide initiatives. This chapter also provides some notes on how to merge this technology with other systems, such as a penetrating spectral device for underground measurements utilizing the catheterization approach.

Soil health assessment: A critical review of current methodologies and a proposed new approach

The wellbeing of soils is crucial for securing food production worldwide. The soil health (SH) concept has been introduced due to an evolving understanding that soil is not just a growing medium for crops but that it provides a foundation for other essential ecosystem services (ES). The SH concept requires development of a holistic index for reliable and quantitative assessment of soil wellbeing related to the effects of different soil management practices and land uses. The aims of this paper are to: (1) review current approaches and methods to assess SH, (2) highlight the role of soil ES in characterizing soil function and (3) propose a new approach to assess SH via monitoring of ES provided by soils. We introduce a brief critical review of the following three main steps required for assessment of common SH indices: (1) selection of relevant attributes; (2) quantification and scoring approaches; and (3) integration of the selected attributes to construct the SH index. These steps usually include statistical or expert opinion-based approaches. In addition, we present a new approach that highlights the relevance and importance of soil ES, i.e., provisioning, regulating and supporting services that must be quantified for comprehensive assessment of soil functions and for fitting models that relate selected soil attributes to ES. This will allow practitioners and scholars to identify the most significant and universal attributes, quantify the relative contribution of each attribute to each ES, and subsequently assess the overall health of soils.

Novel approach for quantitatively estimating element retention and material balances in soil profiles of recharge basins used for wastewater reclamation

We investigated changes in element content and distribution in soil profiles in a study designed to monitor the geochemical changes accruing in soil due to long-term secondary effluent recharge, and its impact on the sustainability of the Soil Aquifer Treatment (SAT) system. Since the initial elemental contents of the soils at the studied site were not available, we reconstructed them using scandium (Sc) as a conservative tracer. By using this approach, we were able to produce a mass-balance for 18 elements and evaluate the geochemical changes resulting from 19 years of effluent recharge. This approach also provides a better understanding of the role of soils as an adsorption filter for the heavy metals contained in the effluent. The soil mass balance suggests 19 years of effluent recharge cause for a significant enrichment in Cu, Cr, Ni, Zn, Mg, K, Na, S and P contents in the upper 4m of the soil profile. Combining the elements lode record during the 19 years suggest that Cr, Ni, and P inputs may not reach the groundwater (20 m deep), whereas the other elements may. Conversely, we found that 58, 60, and 30% of the initial content of Mn, Ca and Co respectively leached from the upper 2-m of the soil profile. These high percentages of Mn and Ca depletion from the basin soils may reduce the soils ability to buffer decreases in redox potential pe and pH, respectively, which could initiate a reduction in the soils holding capacity for heavy metals.